Barbarian: Barbaric Roar decreases enemy defense with 75%.Sorceror: Mirror something steals enemies defense and gives it to youAssassin: PoisonTemplar: You got more health and defense than any enemy (almost) so you'll just have to fight a battle of attrition.

Any class can use the basic poison dagger, not just the Assassin, but only Assassins can use the more advanced poison daggers. Upgrade it at Chappi and it will do 6 damage per turn for several turns. It doesn't sound like much but it really adds up after awhile.